1. Field of the Invention
The present invention relates to a laser microscope which uses a micromirror device.
The present invention also relates to a device for generating line-shaped light beam having a thin elongated cross section, which converts a laser beam emitted from a laser light source into an incoherent line-shaped light beam by use of the micromirror device.
2. Description of the Related Art
There has been known a laser microscope in which a surface of a sample to be observed is scanned two-dimensionally by a laser beam and reflected light from the sample is received by a linear image sensor. In such laser microscope, a laser beam generated from a laser light source is deflected in a main scanning direction at a high speed by an acoustic-optical element and deflected in a sub-scanning direction perpendicular to the main scanning direction using a galvano-mirror, whereby the surface of the sample is two-dimensionally scanned by use of laser beam. The laser microscope can achieve high resolution as it uses a confocal optical system, and it has been used for various purposes in which high-resolution images are required. The laser microscope which uses the confocal optical system also has an advantage that, since the surface of the sample is two-dimensionally scanned, quality of an image to be picked up is not deteriorated even if there is a speckle pattern in the laser beam.
Although the laser microscope using the laser beam has an advantageous effect capable of picking up a high-resolution image, a disadvantage of high manufacturing cost of the microscope has been pointed out, because the cost of the acoustic-optical element which deflects the laser beam in the main scanning direction is extremely high. There has been another disadvantage that because of a relatively small beam deflection angle of the acousto-optic element, an optical path length of the optical system must be made longer in order to obtain a desired scanning length on the sample, and consequently the microscope device has been enlarged.
Further, as the acoustic-optical element has wavelength dependence, acoustic-optical elements having different setting conditions must be prepared for each wavelength of laser beams to be used. For example, in the case of a color microscope, acoustic-optical elements having different set conditions must be prepared for each color light, which has caused high manufacturing costs.
To solve such disadvantages, there has been known a method in which a light beam generated from the laser light source is converted into a rectilinear beam having thin elongated cross section in one direction by using a cylindrical lens and in which the surface of the specimen is scanned by the rectilinear beam. However, in the case of using the rectilinear beam produced by cylindrical lens, because of high coherence of the laser beam, many speckle patterns are generated in the rectilinear beam, and thus a high-quality image cannot be picked up. In this case, a method is available which uses a light source such as a mercury lamp to produce incoherent light beams. However, because the mercury lamp is large in size and high in price, there is a disadvantage that the size of the microscope is enlarged and manufacturing costs become high. Thus, if a light source which generates incoherent line-shaped light beams is developed, it is possible to greatly reduce manufacturing costs of the laser microscope and to miniaturize the structure thereof.